This invention pertains to an apparatus and a method of inserting and removing an active tag into a compartment which is permanently attached to a tire. More particularly, this invention sets forth a method and apparatus for inserting and removing an electronic device encapsulating in a rigid material, into a compartment of a vulcanized rubber patch which is permanently attached to a vulcanized tire.
It is desirable to monitor engineering conditions of tires, such as wear, internal pressure and internal temperature in order to reduce tire costs and maximize vehicle efficiency. Of course, it is advantageous to perform such monitoring in large truck tires, which are expensive.
Prior art methods of monitoring large truck tires have included passive integrated circuits embedded in the body of the tire, or self-powered circuits which are positioned external to the tire. The passive integrated circuits rely on inductive magnetic coupling or capacitative coupling to energize the circuit, thus providing power to the circuit from a source remote from the tire. Self-powered circuits positioned external to the tire are exposed to damage from the environment such as weather, road hazards and even vandalism.
Recent engineering advances have permitted the installation of monitoring devices having active integrated circuits within tires. One such device is described in U.S. Pat. No. 5,562,787 to Koch et al. entitled xe2x80x9cMethod of Monitoring Conditions of Vehicle Tiresxe2x80x9d, incorporated herein by reference, and assigned to the assignee of the present invention. These devices include an active circuit powered by a dedicated long life, miniature battery and at least one senor for detecting, optionally storing and transmitting real time engineering conditions within the tire. Such devices are capable of being programmed to remain in an active, but dormant condition, but will switch automatically to an xe2x80x9cawakenedxe2x80x9d condition in response to an external signal or a condition which exceeds preset limits.
One of the problems faced with such active devices is that they are delicate electronic devices that must operate in the harsh environment of a tire. Thus it is important to secure these devices in the tires to minimize the effect of the harsh tire environment on them, while still permitting them to be exposed to this environment to allow accurate monitoring of the engineering conditions for the life of the tire. These active devices have previously been mounted in tires by first encapsulating the device or power-containing circuit in a material which forms a rigid or semi-rigid encasement about the device, thereby inhibiting straining of the device as a result of applied stresses during operation. Such materials have included non-foam compounds such as urethanes, epoxies, polyester-styrene resins, hard rubber compositions, and the like. The encapsulated device is then placed into a green rubber material which forms a housing or is placed in a green rubber pocket or pouch that becomes part of the tire. The encapsulated device is then permanently set within the rubber material during a subsequent vulcanizing operation. The encapsulated device, including the power source or battery, is then permanently assembled to the tire, so there is no way to replace the battery once it is discharged, nor is there a practical way to disassemble the encapsulated device to repair a failed component.
While the methods and apparatus of U.S. Pat. No. 5,562,787 provide an acceptable method of assembling an active chip into a tire cavity, an improved method and apparatus which permits assembly and disassembly of the encapsulated device and battery from the tire.
In accordance with the present invention, an improved method and apparatus for assembling and disassembling an active electronic monitoring device into a tire is disclosed.
The improved method and apparatus permits the insertion and removal of an electronic monitoring device from a tire, while securing the electronic monitoring device to the tire so that stress, strain, impact, cyclic fatigue and vibration are minimized. A rubber patch having a first side which includes a housing with a cavity having a preselected configuration and a second opposite side approximating the contour of an innerliner of a fire is prepared. Although the rubber patch may be assembled to the tire and vulcanized with the tire, it is much more practical to assemble the rubber patch to the tire after both the rubber patch and the tire have been vulcanized. After the rubber patch is vulcanized, the patch is permanently assembled to the innerliner of a vulcanized tire by affixing the second opposite side of the patch to the tire innerliner. The electronic monitoring device, after having been encapsulated in a suitable rigid potting material to form a rigid tag, is fitted with a power source to form a tag assembly in a shape which allows for insertion into the contour of the cavity housing which is carefully inserted into the cavity housing. The tag assembly is locked into place within the cavity using a suitable removable locking means.
An advantage of the present invention is that the tag assembly may be inserted into the tire after vulcanization of the tire and after the assembly of the patch to the tire. Because the tag assembly is locked into place using removable locking means, the tag assembly may be removed at any time during the life of the tire to replace the rigid tag or the power source. Thus, if a battery fails, it may be easily replaced so that the tag assembly can continue to operate. If the rigid tag fails because of a failure of any of the components comprising the tag, it can easily be removed or replaced.
Another advantage of the present invention is that is a tire is to be retreaded, the tag assembly may be removed from the tire during the vulcanizing operation and replaced after completion of the vulcanizing operation, so that the sensitive and delicate electronic circuitry of the rigid tag and the batter are not subjected to the harsh environment of the vulcanizing operation, which could destroy or adversely affect its life.
Since the tag assembly is removable for repair or replacement, a further advantage is that, in the event of a failure of the battery or any component of the rigid tag, it is not necessary to assemble a second patch assembly to the tire.